Cathode-ray tube having a color-selection electrode with large apertures



H. KAPLAN CATHODE-RAY TUBE HAVING A COLOR-SELECTION ELECTRODE WITH LARGEAPERTURES Filed June 14, 1961 2 Sheets-Sheet 1 TO GREEN 70 REDINVE/VT'OR 36 501277, [17. 76612920127,

ATTORNEY r0 GREEN F1 Q 4! 24 Aug. 25, 1964 s. H. KAPLAN CATHODE-RAY TUBEHAVING A coma-summon ELECTRODE WITH LARGE APERTURES 2 Sheets-Sheet 2 FIG.67)

Filed June 14, 1961 I/VVEIVTOR A T TOR/V5) RED United States Patent3,146,369 CATHODE-RAY TUBE HAVING A COLOR-SELEC- TEON ELECTRODE WITHLARGE APERTURES Sam H. Kaplan, Chicago, 111., assignor to The RaulandCorporation, a corporation of Illinois Filed June 14, 1961, Ser. No.117,060 13 Claims. (Cl. 313--92) The present invention relates generallyto cathode-ray tubes for use in color television receivers and the likeand more particularly to improvements in single-gun cathoderay tubes ofthe simultaneous presentation type for reproducing images in simulatednatural colors.

Cathode-ray tubes of the above-mentioned type usually comprise anevacuated envelope made of glass or any suitable material, having aface-plate provided at the enlarged end of the envelope. An electron gunassembly, provided in the neck portion of the tube, produces an electronbeam, controlled by the deflection means of the tube, to simultaneouslyexcite phosphor areas emitting diiferent colors, three in this case.

The screen comprises a mosaic of a plurality of clusters of elementalphosphor areas adapted to emit light of different colors when excited bythe impinging electron beam.

A color-selection electrode, usually a multi-apertured mask,conventionally made of a thin metal sheet, opaque to the passage ofelectrons, is disposed between the electron gun and the image screen injuxtaposition with the screen. The mask is provided with a plurality ofapertures in registry with and geometrically related in shape to theclusters of phosphor areas on the screen, the apertures being disposedin a selected geometrical array on the mask in registry with thegeometrical array of the clusters of phosphor areas on the mosaic imagescreen of the tube. By controlling the angle of incidence of theelectron beam through the apertures in the mask, the electron beam iscaused to impinge predetermined partial areas of the clusters ofdifferent phosphor areas on the screen, thus producing a predeterminedcolor emission of the selected cluster areas reproducing the originalscene as a visible picture in natural color on the screen.

The simultaneous presentation of the diflerent colors on the mosaicimage screen in a single-gun color cathoderay tube presents numerousproblems. One of the major problems is to ensure the correctregistration of the electron beam onto the mask and the screen toproduce a uniform color reproduction, and to prevent color contaminationof the reproduced image. Another problem is unsatisfactory brightness ofthe reproduced image, which is largely due to low mask transmission forelectrons. Also, due to mechanical, magnetic, thermal and electricaleifects, contamination of the individual colors, including white, mayoccur; this distorts to a substantial degree the presentation of thecolor images on the screen and contributes to the inadequate contrastwhich is characteristic of prior single-gun color tubes. 7

Accordingly, it is a general object of this invention to provide a newand improved cathode-ray tube for reproducing images in simulatednatural color.

Another object of the present invention is to provide an improvedsingle-gun cathode-ray tube for reproducing images in simulated naturalcolor, the reproduced image being of substantially improved brightness.

It is another object of this invention to provide an improved single-guncathode-ray tube for reproducing images in simulated natural color, inwhich the individual colors including white are more accuratelyreproduced.

A further object of the present invention is to provide a new andimproved single-gun cathode-ray tube for reproducing images in simulatednatural color, in which most of the ambient light falling on the imagescreen is effectively absorbed, thus providing materially improvedcontrast in the reproduced image.

A cathode-ray tube for reproducing images in simulated natural color,constructed in accordance with the present invention, comprises a mosaicimage screen comprising a multitude of similar clusters of elementalphosphor areas, each cluster composed of one area of each of a pluralityof phosphors exhibiting different color-radiation in response toelectron bombardment and collectively balanced to produce white lightoutput in response to total-area excitation, and each cluster spacedfrom each adjacent cluster by a distance of at least one third of itsown characteristic transverse dimension; a color-selection electrode, injuxtaposition with the image screen, comprising a correspondingmultitude of apertures, each aligned with one of the clusters and eachaperture being of corresponding shape and at least as large in size asthe cluster with which it is aligned; means for projecting an electronbeam through the apertured color-selection electrode onto the imagescreen; means for modulating the intensity of the electron beam; andmeans for varying the angle of incidence of the electron beam on thecolor-selection electrode to establish total-area excitation of theclusters for white light output and to establish controlled varyingpartial-area excitation of the clusters for different component colorsof the reproduced image.

The inventive arrangement comprises a single-gun tube having acolor-selection electrode referred in the following as a mask andwherein the color deflection device includes two pairs of electrostaticcolor deflection plates at an angle to each other. The tube alsoincludes a mosaic image screen which can be planar or of sphericalconfiguration and may be mounted either on the face-plate of the tube oron a target plate, disposed behind the face-plate. In the embodiment tobe described, the mosaic image screen is disposed on the inside of theface-plate. The screen comprises a multitude of similar clusters ofelemental phosphor areas whereby each cluster is composed of one area ofeach of the plurality of phosphors exhibiting different color radiationin response to the electron bombardment. The arrangement is such thatthe phosphor areas are balanced collectively with respect to each otherto produce White light output in response to the excitation by theelectron beam of the whole area of the cluster.

An important feature of the inventive arrangement is the provision ofintermediate areas surrounding and separating the phosphor cluster.

Another feature of the inventive arrangement is the spacing of thephosphor clusters from each other by at last one third of theirtransverse dimensions. The individual phosphor areas of the clusters maybe of any geometrical nesting configuration: rectangular, circular orhexagonal.

The mask which is positioned in juxtaposition with the screen comprisesa multitude of apertures corresponding and aligned with each of theclusters, the size of the apertures in the mask being at least as largeas the size of the clusters with which these apertures are aligned. Theapertures are'preferably dimensioned to provide an electron beam imageon the image screen, which is equal to or larger than the size of thephosphor clusters.

The electron beam from the electron gun is deviated by the abovementioned electrostatic color deflection electrodes, and is deflected bya yoke member provided in the neck portion of the tube to scan thescreen, to establish total-area excitation of the clusters on the screenfor white light output and partial-area excitation for differentcomponent colors of the clusters by controlled variation of thepartial-area excitation of the clusters. A convergence system forre-converging the electron beam in the plane of the mask or screen isprovided in the tube in conventional manner.

The partial excitation of the respective individual phosphor areas inthe clusters is effected by a corresponding, limited displacement of theelectron beam image on the screen away from the total-area or whiteposition into the intermediate areas between the clusters on the screenin different predetermined radial directions corresponding to therespective position of the individual phosphor areas of different color.

The features of the present invention, which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages thereof, may be bestunderstood, however, by reference to the following description ofexemplary embodiments of this invention taken in connection with theaccompanying drawings, in the several figures of which like referencenumerals identify like elements, and in which:

FIGURE 1 is a schematic view of a single-gun multicolor cathode-ray tubeembodying the invention.

FIGURE 2:! is a fragmentary view of the screen of one of the embodimentsof the present invention in which the clusters are of rectangularconfigmration.

FIGURE 2b is a fragmentary view of a mask used in the cathode-ray tubecomprising the screen of FIG- URE 211.

FIGURE 3 is a fragmentary view of the screen of the inventive tube,showing the relative positioning of a phosphor cluster and thecorresponding location of the electron beam image on the screen inwriting a pure red color.

FIGURE 4 is a fragmentary view of the screen in which the location ofthe electron beam image on the screen is shown relative to a number ofadjacent clusters when a pure green color is being written.

FIGURE 5 is a fragmentary view of another embodiment, in Which thescreen comprises a phosphor cluster in which the individual areas ofdifferent phosphors are of different size and are spaced from eachother.

FIGURE 6a is a fragmentary view of a screen showing a pattern of theclusters employed in prior art color tubes in which the clusters and theindividual phosphor areas are of circular configuration.

FIGURE 6b is a fragmentary view of the screen of a tube embodying theinvention and comprising circular clusters.

FIGURE 60 is a fragmentary view of the screen, similar to that of FIGURE6b, but with the clusters shaped and disposed to provide higherefficiency.

FIGURE 7a is a fragmentary view of the screen of a further embodiment ofthe present invention, in which the phosphor clusters are of hexagonalconfiguration.

FIGURE 7b is a fragmentary view of a screen similar to that of FIGURE7a, but with the phosphor clusters arranged to provide improvedefliciency.

FIGURES 8a and 8b are schematic views showing two preferred types ofdistribution array of clusters on the screen of a color tube embodyingthe invention.

A color reproducing cathode-ray tube 20 having a glass envelope 21 isshown in FIGURE 1. For clarity, most of the physical details, which donot relate to the present invention, are omitted. The single electrongun is indicated by a rectangle 22 which is disposed in the neck portion23 of the cathode-ray tube envelope 21. The electron gun is arranged toemit an electron beam W which is accelerated in known manner and passesthrough a deflection field produced by scanning signals applied to ayoke member 27. This deflection field changes the course of the electronbeam in accordance with the instantaneous sweep signals applied to theyoke member 27. Such course change of the electron beam is gradualwithin the deflection field; for purpose of illustration, however, thechange of the course of the electron beam is shown as occurring in aplane a-a passing through the yoke member 27. After being deflected, theelectron beam W is directed through the apertures in the colorselectionelectrode or mask 28 to impinge on the scanning side (the side on whichthe electron beam components are incident) of the image mosaic screen24.

The cathode-ray tube 20 is also provided in known manner with aconvergence system, represented in the drawing by a convergence yokeassembly 27a, for converging the electron beam both statically anddynamically in the plane of the mask 28. The mask structure 28 isprovided with a plurality of apertures 30, the screen 24 being coveredwith a corresponding plurality of phosphor clusters 31. An electrontransparent aluminum or other conductive, reflective layer 50,preferably, covers in conventional manner the entire rear surface of thescreen to improve the brightness, and to apply an operational potentialto the screen. Three interspersed similar groups of phosphor areas, onefor each primary color, are provided on the screen, and adjacentphosphor areas, one from each group, constitute the respective clustersor triads 31. The phosphor areas and thus the apertures in the mask maybe of circular configuration as in conventional shadow mask tubes, butother shapes of the phosphor areas on the screen and of the apertures inthe mask are feasible, as for instance, rectangular, square andhexagonal.

The different groups of phosphor areas on the screen 24, regardless oftheir configuration, possess different color-response characteristics,each group emitting light of a different one of the elemental or primarycolors when excited by the electron spot. Different phosphor materialsare used for producing the elemental colors green, blue and red. Theconstruction of the tube as thus far described, and the manner of itsconstruction are well known in the art.

In accordance with the present invention the control of the colorpresentation in a single-gun tube, using a simultaneous type ofpresentation, is effected by means of a subtractive area approach. Tothis end, apertures 30 in mask 28 are individually made larger than theassociated individual clusters of phosphor areas, and intermediateinactive spaces or dead areas are provided between adjacent phosphorclusters. FIGURE 2a shows the phosphor cluster 31 of generally squareconfiguration positioned on the image screen 24 in such a manner thateach cluster 31 is separated from all adjacent clusters by intermediatenon-phosphor coated areas of approximately one half the width of anindividual cluster 31. Each cluster is composed of phosphor areas R, Band G for producing red, blue and green light respectively, the redphosphor areas R being larger than the blue and green areas B and G tocompensate for the lower conversion efliciency of known red phosphormaterials. FIGURE 2b shows apertures 30 individually of substantiallythe same size as the individual clusters 31, or slightly larger, and ofcorresponding configuration. Each aperture 30 in mask 28 is aligned witha phosphor cluster 31 on screen 24.

When the electron beam W is not deflected by the color deflection platepairs 25 and 26 the electron spots are centered on the phosphor clusters31, providing totalarea excitation thereof and producing pure whitesince the sectional areas of different colors of the cluster areproportioned relative to the respective phosphor efliciencies to bebalanced for white.

For producing different colors, the electron beam passing through therespective aperture in the mask, is deflected under the control of colorselection plates 25, 26 to direct the electron spot partially into theintermediate area between the phosphor clusters; the electron spot isthus positioned in part on the section of the phosphor cluster of apredetermined, individual color and in part in the intermediate deadarea to provide controlled partial-area excitation of the phosphorclusters, the in ter-cluster spacings being made sufiiciently large toenable the presentation of a pure color which is not contaminated by theplacement of the electron spot on any section of the adjacent phosphorclusters.

According to a further feature of this invention, the whole intermediatearea 32 between the phosphor clusters 31 is preferably occupied by alight absorbing material.

The color-selection process may more readily be visualized from aconsideration of FIGURE 3 in which the positions of the electron spot33, relative to the individual sections of diflerent color of thephosphor cluster 31, are indicated for white or monochrome reproduction,and for a pure component color respectively. When the beam isundeflected by deflection plates 25, 26, the electron spot 33 iscentered on cluster 31 to provide total-area excitation thereof andproduce white light. For a pure red component, the electron spot isdeflected to the position designated 33r in which only the red phosphorcomponent 36 of the cluster 31 is excited, the remaining portion of theelectron spot overlapping on the intermediate area 32 separating theadjacent clusters.

In order to obtain a pure green color, the electron spot is displaced tothe position 33g, shown in FIGURE 4 in which only the green phosphorarea 34 is excited, the remaining portion of the electron spotoverlapping the intermediate space 32 between the energized cluster andthe two adjacent clusters. In similar manner, a pure blue color isobtained by corresponding displacement of the electron spot to the leftand downwardly from its neutral position 33.

Intermediate colors such as yellow, cyan, magenta and others areobtained by appropriately controlled displacement of the electron spotin other directions; for instance, for the cyan-color the electron spotis shifted to the left of its neutral or white position 33. For pastelcolors the displacement of the electron spot is in the direction of thedominant hue.

It should be noted that although three directions of color deflectionare needed for presentation of the three elemental colors, only two setsof plates are necessary since the net desired displacement of theelectron spot can always be resolved into two mutually orthogonaldisplacements. Appropriate apparatus for developing the requiredcolor-control signals for application to deflection plates 25, 26 may bethe same as that employed in conjunction with other single-gun colortubes and is well known in the art; see for example the October 1951issue of the Proceedings of the Institute of Radio Engineers, on pages1195, 119-8 and 1200 of the article entitled A One Gun Shadow Mask ColorKinescope by R. R. Law.

It is known in the art that substantial difiiculties are encountered inthe precise positioning of the electron spot relative to the location ofthe phosphor clusters on the screen. These irregularities in theelectron beam landings are due to small variations of the environmentalmagnetic fields, thermal expansions, mechanical factors etc. The exactpositioning of the electron spot is also influenced by variations in theaperture sizes, variable spacings between the mask and the screen andvariable sizes of the phosphor areas on the screen due to exposurevariations in the screen fabrication process, as well as to possibleerrors in the convergence system. In order to compensate for suchirregularities of the electron beam landings, tolerances are provided bymaking the apertures 30 in mask 28 slightly larger than the phosphorclusters 31. In this manner, it is ensured that slight displacements ofthe location of the electron spot 33 on the screen will not produce anyundesirable changes in color presentations, thus compensating for theabove mentioned irregularities and enabling pure whites to be obtainedover the entire screen.

In a further and preferred arrangement shown in FIG- URE 5, tolerancebands or intermediate inactive areas 38 are also provided between theindividual color sections 34, 35 and 36 of the phosphor clusters 31 onthe screen. These tolerance band spacings serve to provide tolerance forboth white and saturated colors so that minor beam landing errors, dueto various eflects previously mentioned,

cause little or no error in reproduced colors. This enables a puresaturated color presentation of the different individual color areas,which further improves the quality of the image on the screen.

FIGURE 6a of the drawings shows the distribution of the phosphorclusters on the screen in a simultaneous presentation one-gun colorcathode-ray tube of a type known in the art, indicating phosphor dots ofcircular configuration. In such prior art devices, the aperture size isconsiderably smaller than the area of the individual phosphor dots, andhence much smaller than the individual phosphor clusters. Specifically,the individual apertures should not be greater than the diameter of theindi vidual phosphor areas in order to avoid color contamination. Thisresults in a mask transmission factor approximately 44% less than thatprovided in a tube embodying the present invention, which means that thebrightness of a reproduced monochrome image is improved by acorresponding factor by employing the improved tube described herein.

Furthermore, the color circuitry required to achieve comparable colorbalance with the prior art mask and screen configuration issubstantially more complicated due to the fact that, as the electronbeam is deviated in any given color direction, the area of the electronspot on the dominant color increases and this increases the light outputof that color. The color deflection means thus not only changes therespective color, but also its brightness so that it becomes desirableto reduce the electron beam current proportionately as purer colors arewritten. The present invention obviates the need for any such dynamicbeam current control, by the use of subtractive area color control andthe provision of intermediate dead spaces or tolerance bands 32 as shownin FIGURE 612, from which it can readily be seen that variation in spotsize as a function of color-control deviation cannot increase the areaof component color excitation for even a pure primary color beyond thatobtained with the undeviated electron spot.

The provision of the intermediate inactive areas 32 between the phosphorclusters also permits new and more highly eflicient geometricalarrangements of the array of the phosphor clusters on the screen.

In accordance with another feature of the present invention, the size ofthe phosphor clusters may be increased without increasing the spacingsbetween clusters. This can be accomplished by a predetermined rotationof the individual phosphor clusters with respect to the array. Thedisplacement of the electron beam for writing pure colors of the threeadjacent clusters is thus also shifted and now some portions of theintermediate space between these clusters are utilized for receivingunused portions of the electron spot in writing two or three differentcolors. This reduction of the intermediate spaces between the phosphorclusters, by having such spaces serve double or triple duty,substantially increases the brightness of the tube; in any event,however, the spacing between adjacent clusters must be greater thanone-third the characteristic transverse dimension of an individualcluster.

Such an improved array is shown in FIGURE 60, in which the area Qbetween the centrally disposed phosphor cluster X and two adjacentphosphor clusters Y and Z to its right is utilized for receiving unusedportions of the electron spot during blue-color excitation of the upperright cluster Y, green-color excitation of the center cluster X, andred-color excitation of cluster Z.

FIGURE 7a shows a modification of the arrangement of FIGURE 6b but withhexagonal apertures and cluster configuration; FIGURE 7b shows amodified array of hexagonal apertures and clusters, with a common area ibetween three adjacent phosphor clusters used for receiving the unusedportions of the electron spots during red-, green-, and blue-colorexcitation respectively.

The contrast characteristics of the tube can be further improved and theambient light reflections on the surface ale-e369 of the screen can besubstantially reduced by blackening the intermediate areas 32 betweenthe phosphor clusters; this may most conveniently be accomplished bycoating these intermediate areas with a light absorbing material such asblack manganese dioxide or finely divided silver particles. Theseblackened intermediate areas of the image screen substantially reducethe ambient light reilections by effectively absorbing the ambient lightbut do not attenuate the light emitted by the image screen.

Moreover, the blackening of the inactive areas intermediate the phosphorclusters permits the utilization of a clear glass face-plate 30 andclear glass safety-plate 40 (FIGURE 1) rather than the darkened glassconventionally used in television picture tubes, which further increasesthe brightness of the tube without loss of contrast and in manyinstances with improved contrast as well.

A further advantage consists in this, that desaturation effects causedby reflected ambient light are reduced by the increased effectiveabsorption of this ambient light by the intermediate black areas betweenthe phosphor clusters; this also improves the contrast ratios obtainablein the reproduced image without reducing the efiiciency of thecathode-ray tube.

A preferred method of making the screen with blackened intermediateareas will now be described. The blackened areas should be screenedfirst; different methods for producing the light absorbing surfacesbetween the phosphor areas of the image screen may be employed. Forexample, the black areas may be produced by coating the screen surfacewith a high contrast type silver halide emulsion, exposing this surfaceto light through the apertures in the mask, and then processing theexposed emulsion to yield a direct positive image, whereby all areaswhich are not struck by the light will exhibit a black silver image, andthe areas struck by the light will be clear for receiving the desiredphosphors. Then the different color phosphor areas are produced by anywell known photoscreening technique, for instance, the conventionalphos- .phor slurry process. In accordance with the respective color tobe screened, the light source used in the photoscreening is displaced;in each exposure, the light is directed partly on the blackened area andpartly on the desired portions of the clear areas. The phosphor adheresonly in the respective areas struck by the light, thus producingphosphor areas partly on the blackened intermediate areas and partly inthe clear areas. This procedure is repeated for the other two colors.

In operation of the tube, when a phosphor cluster is excited by theelectron spot, light emitted by any portion of the phosphor areapositioned over the blackened intermediate areas is effectively absorbedby the black particles underneath the phosphor coating and does notreach the observer. Only the light produced by the excited portions ofthe phosphor superposed on the clear areas is seen.

It should be noted that the use of certain configurations or patterns ofphosphor clusters on the screen may result in the production of a moreor less prominent beat pattern or moire between the scanning lines andthe phosphor cluster pattern. In accordance with a further embodiment ofthe present invention undesirable moir effects are minimized byemploying an orientation or pattern in which the phosphor clusters arestaggered relative to each other as in FIGURE 8a, and/ or rotatedapproximately 45 degrees relative to the scanning lines as in FIGURE 8b.

In an illustrative cathode-ray tube for reproducing images in simulatednatural color, comprising a screen of the type shown in FIGURE 5, thearea of red phosphor such as zinc phosphate, manganese activated, may be0.012 x 0.0255 inch; the area of the green phosphor such as zincsilicate, manganese activated, is 0.012 x 0.0135 inch and the area ofthe blue phosphor such as zinc sulfide, silver activated, is 0.012 x0.0115 inch, the tolerance bands being all of the same width of 0.0015inch. For

this cluster the projected size of the mask aperture is .0285 x .0285inch with horizontal aperture spacings of .01425 inch and verticalseparations of .01575 inch. The area of each phosphor cluster, includingthe adjoining inactive or dead spaces between itself and adjacentclusters, is .04275 x .04425 inch. It should be noted that no movementof the entire electron image on the screen changes the white colorunless it exceeds the width of the tolerance band of 0.0015 inch.

In the phosphor system of the illustrated cathode-ray tube, the ratio ofred phosphor area to total screen surface and therefore the percentageof the total beam current used for red phosphor excitation (since eachred area is totally energized for a pure red color field), is equal toSince 68% of the total-area of the screen does not have any phosphor(the blackened intermediate areas), the need for the usual 70% filteraction of the conventional faceplate of the tube is eliminated. The redoutput (which is a measure of useable brightness in such tubes) of theinventive tube is approximately equal to 16.2%. For comparison purposesa conventional three-gun shadow mask tube with 0.012 inch apertures and0.028 inch spacing in a triangular type array, has a transmission of16.6% which corresponds to the red brightness available; use of a 70%filter face-plate reduces this to about 11.6% (.7 x 16.6:11.6). Thus thetotal effective brightness of the inventive single-gun subtractive areatube may exceed that of a conventional three-gun shadow mask tube byapproximately 40%. Considering further the elimination of the filteringaction of the safety-glass which the blackened areas permit, theinventive tube may provide a picture as much as brighter than theconventional three-gun shadow mask tube.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and, therefore, the aim in the appended claims isto cover all such changes and modifications as fall within the truespirit and scope of the invention.

I claim:

1. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting different color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to total area excitation, and eachcluster spaced from each adjacent cluster by a distance of at leastone-third of its own characteristic transverse dimension; acolor-selection electrode, in juxtaposition with said image screen,comprising a corresponding multitude of apertures each aligned with oneof said clusters and each aperture being of corresponding shape and atleast as large in size as the cluster with which it is aligned; meansfor projecting an electron beam through said apertured color-selectionelectrode onto said image screen; means for modulating the intensity ofsaid electron beam; and means for varying the angle of incidence of saidelectron beam on said colorselection electrode to establish total-areaexcitation of said clusters for white light output and to establishcontrolled varying partial-area excitation of said clusters fordifferent component colors of said reproduced image.

2. A cathode-ray tube for reproducing images in simulated natural coloras in claim 1, in which the shapes of said clusters of elementalphosphor areas on said screen and said apertures in the color-selectionelectrode are substantially circular.

3. A cathode-ray tube for reproducing images in simulated natural coloras in claim 1, in which said clusters of elemental phosphor areas onsaid screen, the individual elemental phosphor areas of said clusters,and the aper-l tures in said color-selection electrode are ofrectangular configuration.

4. A cathode-ray tube for reproducing images in simulated natural coloras in claim 1, in which said clusters of elemental phosphor areas onsaid screen and the apertures in said color-selection electrode are ofhexagonal configuration.

5. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting different color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to total-area excitation, each clusterspaced from each adjacent cluster by intermediate light absorbing areasof a width equal to at least one-third of the transverse dimension ofthe individual clusters; a color-selection electrode, in juxtapositionwith said image screen, comprising a corresponding multitude ofapertures each aligned With one of said clusters and each aperture beingof corresponding shape and at least as large in size as the cluster withwhich it is aligned; means for projecting an electron beam through saidapertured color-selection electrode onto said image screen; means formodulating the intensity of said electron beam; and means for varyingthe angle of incidence of said electron beam on said colorselectionelectrode to establish total-area excitation of said clusters for whitelight output and to establish controlled varying partial-area excitationof said clusters for difierent component colors of said reproducedimage.

6. A cathode-ray tube for reproducing images in simulated natural coloras in claim 5, in which said mosaic image screen is disposed on theinside surface of a transparent, clear glass face-plate of saidcathode-ray tube.

7. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting different color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to totalarea excitation and each clusterspaced from each adjacent cluster by an intermediate area adequate forthe displacement of the deflected electron beam to establish aparticular area of excitation for the pure color components in saidcluster without overlapping phosphor areas of the adjacent clusters; acolor-selection electrode, in juxtaposition with said image screen,comprising a corresponding multitude of apertures each aligned with oneof said clusters and each aperture being of corresponding shape and atleast as large in size as the cluster with which it is aligned; meansfor projecting an electron beam through said apertured color-selectionelectrode onto said image screen; means for modulating the intensity ofsaid electron beam; and means for varying the angle of incidence of saidelectron beam on said color-selection electrode to establish total-areaexcitation of said clusters for white light output and to establishcontrolled varying partialarea excitation of said clusters for differentcomponent colors of said reproduced image.

8. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting different color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to total-area excitation and each clusterspaced from each adjacent cluster by a distance of at least one-third ofits own characteristic transverse dimension; a color-selectionelectrode, in juxtaposition with said image screen, comprising acorresponding multitude of apertures each aligned with one of saidclusters and each aperture being of corresponding shape and at least aslarge in size as the cluster with which it is aligned; means forprojecting an electron beam through said apertured color-selectionelectrode onto said image screen; means for modulating the intensity ofsaid electron beam; and means for varying the angle of incidence of saidelectron beam on said color-selection electrode to establish total-areaexcitation of said clusters for white light output and to establishcontrolled varying partial-area excitation of said clusters fordifferent component colors of said reproduced image; the clusters ofsaid elemental phosphor areas on the screen in registry with theapertures in said color-selection electrode being separated from eachother by an intermediate area ade quate for the displacement of thedeflected electron beam components establishing a particular area ofexcitation for the pure color components in said cluster withoutoverlapping phosphor areas of the adjacent clusters; portions of saidintermediate space between adjacent clusters consecutively receivingdifferent sections of said electron beam as it is deflected between suchdifferent adjacent clusters to excite differently oriented individualphosphor areas thereof.

9. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting diiferent color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to total-area excitation, and eachcluster spaced from each adjacent cluster by a distance of at leastone-third of its own characteristic transverse dimension; acolor-selection electrode, in juxtaposition with said image screen,comprising a corresponding multitude of apertures each aligned with oneof said clusters and each aperture being of corresponding shape andlarger in size than the cluster with which it is aligned; means formaintaining said colorselection electrode and said mosaic image screenat substantially the same potential; means for projecting an electronbeam through said apertured color-selection electrode onto said imagescreen; means for modulating the intensity of said electron beam; andmeans for varying the angle of incidence of said electron beam on saidcolor-selection electrode to establish controlled varying partial-areaexcitation for different component colors of said reproduced image.

10. A cathode-ray tube for reproducing images in simulated natural colorcomprising: a mosaic image screen comprising a multitude of similarclusters of elemental phosphor areas, each cluster composed of one areaof each of a plurality of phosphor exhibiting diflerent color radiationin response to electron bombardment and collectively balanced to producewhite light output in response to total-area excitation; each of saidelemental phosphor areas having a conversion efficiency diiferent thanthose of the other elemental phosphor areas in the same cluster, thesizes of the elemental phosphor areas in each cluster being an inversefunction of their respective conversion efliciencies, and each clusterbeing spaced from each adjacent cluster by a distance of at leastone-third of its own characteristic transverse dimension; acolor-selection electrode, in juxtaposition with said image screen,comprising a corresponding multitude of apertures each aligned with oneof said clusters and each aperture being of corresponding shape and atleast as large in size as the cluster with which it is aligned; meansfor projecting an electron beam through said apertured color-selectionelectrode onto said image screen; means for modulating the intensity ofsaid electron beam; and means for varying the angle of incidence of saidelectron beam on said colorselection electrode to establish total-areaexcitation of said clusters for white light output and to establishcontrolled varying partial-area excitation of said clusters fordifferent component colors of said reproduced image.

11. A cathode-ray tube for reproducing images in comprising a multitudeof similar clusters of elemental phosphor areas, each cluster composedof one area of each of a plurality of phosphor exhibiting differentcolor radiation in response to electron bombardment and collectivelybalanced to produce white light output in response to total-areaexcitation, each of said elemental phosphor areas in each of saidclusters being separated from each other, and each cluster spaced fromeach adjacent cluster by a distance of at least one-third of its owncharacteristic transverse dimension; a color-selection electrode, injuxtaposition with said image screen, comprising a correspondingmultitude of apertures each aligned with one of said clusters and eachaperture being of corresponding shape and at least as large in size asthe cluster with which it is aligned; means for projecting an electronbeam through said apertured color-selection electrode onto said imagescreen; means for modulating the intensity of said electron beam; andmeans for varying the angle of incidence of said electron beam on saidcolor-selection electrode to establish total-area excitation of saidclusters for white light output and to establish controlled varyingpartialarea excitation of said clusters for diiferent component colorsof said reproduced image.

12. A cathode-ray tube for reproducing images in simu- 12 lated naturalcolor as in claim 11, in which the intermediate spaces between saidelemental phosphor areas are occupied with a light absorbing material.

13. In combination: a mosaic image screen and a multiaperturedcolor-selection electrode for color cathode-ray tubes; said mosaic imagescreen comprising a multitude of similar clusters of elemental phosphorareas, each cluster composed of one area of each of a plurality ofphosphor exhibiting different color radiation in response to electronbombardment and collectively balanced to produce white light output inresponse to total-area excitation, each cluster being spaced from eachadjacent cluster by a distance of at least one-third of its owncharacteristic transverse dimension and the components of each clusterbeing spaced from one another, and said color-selection electrodedisposed in juxtaposition with said image screen comprising acorresponding multitude of apertures each aligned with one of saidclusters and each aperture being of corresponding shape and at least aslarge in size as the cluster with which it is aligned.

References Cited in the file of this patent UNITED STATES PATENTS Re.23,838 Rajchman June 8, 1954

1. A CATHODE-RAY TUBE FOR REPRODUCING IMAGES IN SIMULATED NATURAL COLORCOMPRISING: A MOSAIC IMAGE SCREEN COMPRISING A MULTITUDE OF SIMILARCLUSTERS OF ELEMENTAL PHOSPHOR AREAS, EACH CLUSTER COMPOSED OF ONE AREAOF EACH OF A PLURALITY OF PHOSPHOR EXHIBITING DIFFERENT COLOR RADIATIONIN RESPONSE TO ELECTRON BOMBARDMENT AND COLLECTIVELY BALANCED TO PRODUCEWHITE LIGHT OUTPUT IN RESPONSE TO TOTAL AREA EXCITATION, AND EACHCLUSTER SPACED FROM EACH ADJACENT CLUSTER BY A DISTANCE OF AT LEASTONE-THIRD OF ITS OWN CHARACTERISTIC TRANSVERSE DIMENSION; ACOLOR-SELECTION ELECTRODE, IN JUXTAPOSITION WITH SAID IMAGE SCREEN,COMPRISING A CORRESPONDING MULTITUDE OF APERTURES EACH ALIGNED WITH ONEOF SAID CLUSTERS AND EACH APERTURE BEING OF CORRESPONDING SHAPE AND ATLEAST AS LARGE IN SIZE AS THE CLUSTER WITH WHICH IT IS ALIGNED; MEANSFOR PROJECTING AN ELECTRON BEAM THROUGH SAID APERTURED COLOR-SELECTIONELECTRODE ONTO SAID IMAGE SCREEN; MEANS FOR MODULATING THE INTENSITY OFSAID ELECTRON BEAM; AND MEANS FOR VARYING THE ANGLE OF INCIDENCE OF SAIDELECTRON BEAM ON SAID COLORSELECTION ELECTRODE TO ESTABLISH TOTAL-AREAEXCITATION OF SAID CLUSTERS FOR WHITE LIGHT OUTPUT AND TO ESTABLISHCONTROLLED VARYING PARTIAL-AREA EXCITATION OF SAID CLUSTERS FORDIFFERENT COMPONENT COLORS OF SAID REPRODUCED IMAGE.